On April 7–8, 2014, the European Hydration Institute hosted a small group of experts at Castle Combe Manor House, United Kingdom, to discuss a range of issues related to human hydration, health, and performance. The meeting included 18 recognized experts who brought a wealth of experience and knowledge to the topics under review. Eight selected topics were addressed, with the key issues being briefly presented before an in-depth discussion. Presented here is the executive summary and conclusions from this meeting.

Participants (N=34) undertook a CANTAB battery on two separate occasions after fasting and abstaining from fluid intake since the previous evening. On one occasion they were offered 500 ml water shortly before testing, and on the other occasion no water was consumed prior to testing. Reaction times, as measured by Simple Reaction Time (SRT), were faster on the occasion on which they consumed water. Furthermore, subjective thirst was found to moderate the effect of water consumption on speed of responding. Response latencies in the SRT task were greater under the “no water” condition than under the “water” condition, but only for those participants with relatively high subjective thirst after abstaining from fluid intake overnight. For those participants with relatively low subjective thirst, latencies were unaffected by water consumption, and were similarly fast as those recorded for thirsty participants who had consumed water. These results reveal the novel finding that subjective thirst moderates the positive effect of fluid consumption on speed of responding. The results also showed evidence that practice also affected task performance. These results imply that, for speed of responding at least, the positive effects of water supplementation may result from an attenuation of the central processing resources consumed by the subjective sensation of thirst that otherwise impair the execution of speeded cognitive processes.

Research has shown that water supplementation positively affects cognitive performance in children and adults. The present study considered whether this could be a result of expectancies that individuals have about the effects of water on cognition. Forty seven participants were recruited and told the study was examining the effects of repeated testing on cognitive performance. They were assigned either to a condition in which positive expectancies about the effects of drinking water were induced, or a control condition in which no expectancies were induced. Within these groups, approximately half were given a drink of water, while the remainder were not. Performance on a thirst scale, letter cancellation, digit span forwards and backwards and a simple reaction time task was assessed at baseline (before the drink) and 20 minutes and 40 minutes after water consumption. Effects of water, but not expectancy, were found on subjective thirst ratings and letter cancellation task performance, but not on digit span or reaction time. This suggests that water consumption effects on letter cancellation are due to the physiological effects of water, rather than expectancies about the effects of drinking water.

This paper addresses a gap in the literature on the effects of water supplementation on visual attention and motor performance in schoolchildren. There has been extensive research showing that dehydration in adults is associated with detrimental effects on cognitive performance. Furthermore, studies of schoolchildren found that those that arrived at school with a hydration deficit performed worse in cognitive tasks than those children who were better hydrated (see Edmonds, 2012, for review). This is a concern because a recent study of 452 UK schoolchildren, aged between 9 and 11 years old, suggested that 60% of children arrive at school insufficiently hydrated (Barker et al, 2012). These results are consistent with similar studies from France and Israel in which two thirds of the children, of the same age, were insufficiently hydrated at the beginning of the school day (Bonnet et al, 2012; Edmonds, 2012).

http://sheu.org.uk/sites/sheu.org.uk/files/imagepicker/1/eh303pb.pdf

Edmonds, C.J. (2010). Does having a drink of water help children think? A summary of some recent findings. School Health, 6(5), 58–60.

Water is the optimal drink for both adults and children. New guidelines specify how much children should drink during the day. Children are at greater risk of dehydration than adults. While English schools must legally provide drinking water for children, they differ in how they put this legislation into practice. Some schools allow children to have drinking water on their desks, while others restrict access. There are links between the type of access and the hydration state of children. In adults, there are well established links between dehydration and negative effects on cognitive performance. Recent studies suggest that dehydrated children also perform poorly on cognitive tests. More recent research has found that giving children a drink of water improved their cognitive performance on tests of memory, attention, and visual search tasks. These positive effects on cognition are likely to underpin positive effects on academic performance and providing regular access to drinking water in schools would be a cheap and easy way to improve children’s school performance. Further research is indicated to confirm the role of hydration in improving cognition in a UK population and to explore the links to academic and behavioural outcomes.

Edmonds, C.J. & Jeffes, B. Does having a drink help you think? 6–7 year old children show improvements in cognitive performance from baseline to test after having a drink of water. Appetite, 53, 469-472.

Little research has examined the effect of water consumption on cognition in children. We examined whether drinking water improves performance from baseline to test in 23 6-7 year old children. There were significant interactions between time of test and water group (water/no water), with improvements in the water group on thirst and happiness ratings, visual attention and visual search, but not visual memory or visuomotor performance. These results indicate that even under conditions of mild dehydration, not as a result of exercise, intentional water deprivation or heat exposure, children’s cognitive performance can be improved by having a drink of water.

Edmonds, C.J. & Burford, D. (2009). Should children drink more water? The effects of drinking water on cognition in children. Appetite, 52, 776-779.

While dehydration has well-documented negative effects on adult cognition, there is little research on hydration and cognitive performance in children. We investigated whether having a drink of water improved children’s performance on cognitive tasks. Fifty-eight children aged 7-9 years old were randomly allocated to a group that received additional water or a group that did not. Results showed that children who drank additional water rated themselves as significantly less thirsty than the comparison group (p = .002), and they performed better on visual attention tasks (letter cancellation, p = .02; spot the difference memory tasks, p’s = .019 and .014).http://dx.doi.org/10.1016/j.appet.2009.02.010

We explored whether caffeine, and expectation of having consumed caffeine, affects attention, reward responsivity and mood using double-blinded methodology. 88 participants were randomly allocated to ‘drink-type’ (caffeinated/decaffeinated coffee) and ‘expectancy’ (told caffeinated/told decaffeinated coffee) manipulations. Both caffeine and expectation of having consumed caffeine improved attention and psychomotor speed. Expectation enhanced self-reported vigour and reward responsivity. Selfreported depression increased at post-drink for all participants, but less in those receiving or expecting caffeine. These results suggest caffeine expectation can affect mood and performance but do not support a synergistic effect.

Aluminium is the most common metallic element, but has no known biological role. It accumulates in the body when protective gastrointestinal mechanisms are bypassed, renal function is impaired, or exposure is high – all of which apply frequently to preterm infants. Recognised clinical manifestations of aluminium toxicity include dementia, anaemia and bone disease. Parenteral nutrition (PN) solutions are liable to contamination with aluminium, particularly from acidic solutions in glass vials, notably calcium gluconate. When fed parenterally, infants retain >75% of the aluminium, with high serum, urine and tissue levels. Later health effects of neonatal intravenous aluminium exposure were investigated in a randomised trial comparing standard PN solutions with solutions specially sourced for low aluminium content. Preterm infants exposed for >10 d to standard solutions had impaired neurologic development at 18 months. At 13–15 years, subjects randomised to standard PN had lower lumbar spine bone mass; and, in non-randomised analyses, those with neonatal aluminium intake above the median had lower hip bone mass. Given the sizeable number of infants undergoing intensive care and still exposed to aluminium via PN, these findings have contemporary relevance. Until recently, little progress had been made on reducing aluminium exposure, and meeting Food and Drug Administration recommendations (<5 μg/kg per d) has been impossible in patients <50 kg using available products. Recent advice from the UK Medicines and Healthcare regulatory Authority that calcium gluconate in small volume glass containers should not be used for repeated treatment in children <18 years, including preparation of PN, is an important step towards addressing this problem.

Objective: Given the adverse neurobiological effects of suboptimal nutrition on the developing brain, it is of social and medical importance to determine if the global prevalence of poor intrauterine growth causes lasting cognitive deficits. We examined whether suboptimal intrauterine growth relates to impaired cognitive outcome by comparing birth weight and cognition in monozygotic twins and considered whether within-pair differences in birth weight were related to within-pair differences in IQ scores.

Methods: A total of 71 monozygotic twin pairs (aged 7 years 11 months to 17 years 3 months) participated. The Wechsler Intelligence Scales for Children, Third Edition, was administered and verbal IQ (VIQ) and performance IQ (PIQ) scores were calculated. Regression was used to relate within-pair differences in birth weight to within-pair differences in IQ scores.

Results: VIQ but not PIQ score was affected by prenatal growth restriction. The results suggested that the mean advantage for heavier twins relative to their lighter co-twins can be as much as half an SD in VIQ points. In pairs with minimal discordance, heavier twins had lower VIQ scores than their lighter co-twins.

Conclusions: Our study results suggest that lower birth weight in monozygotic twins can also have a negative long-term impact on cognition both in infants who are small at birth and also those with birth weights across the spectrum. Studying monozygotic twins enabled us to examine the effect of reduced intrauterine growth on cognition independently of confounding factors, including parent IQ and education, and infant gender, age, genetic characteristics and gestation.

Objective: Aluminum has known neurotoxicity and may impair shortterm bone health. In a randomized trial, we showed reduced neurodevelopmental scores in preterm infants who were previously exposed to aluminum from parenteral nutrition solutions. Here, in the same cohort, we test the hypothesis that neonatal aluminum exposure also adversely affects long-term bone health, as indicated by reduced bone mass.

Methods:Bone area (BA) and bone mineral content (BMC) of lumbar spine, hip, and whole body were measured with dual radiograph absorptiometry in 13- to 15-year-olds who were born preterm and randomly assigned standard or aluminum-depleted parenteral nutrition solutions during the neonatal period.

Conclusions:Neonates who are exposed to parenteral aluminum may have reduced lumbar spine and hip bone mass during adolescence, potential risk factors for later osteoporosis and hip fracture. These findings need confirmation in larger, more detailed studies. Nevertheless, given our previous finding of adverse developmental outcome in these individuals and the sizeable number of contemporary infants who undergo intensive neonatal care and are still exposed to aluminum via parenteral feeding solutions, the potential adverse longterm consequences of early aluminum exposure now deserve renewed attention.

We studied the age-related differences in inspection time and multiple cognitive domains in a group of monozygotic (MZ) and dizygotic (DZ) twins aged 7 to 17 years. Data from 111 twin pairs and 19 singleton siblings were included. We found clear age-related trends towards more efficient visual information processing in older participants. There were substantial correlations between inspection time and cognitive abilities. The heritability of inspection time was 45%, and ranged from 73% to 85% for cognitive abilities. There were significant non-shared environmental effects on inspection time and Wechsler IQ scores, but no shared environmental effects. The genetic correlation between inspection time and Performance IQ was .55 and with Verbal IQ it was .28. There was a significant non-shared environmental correlation of .24 between inspection time and Verbal IQ.http://dx.doi.org/10.1016/j.intell.2007.05.004

Although IQ is thought to remain relatively stable in the normal population, a decline in IQ has been noted in children born preterm. It is not clear, however, to what extent the inclusion of children with clear neurological damage has influenced these findings. We examined IQ scores obtained in childhood and then again in adolescence from a group of children born at 30 weeks gestation or less who had been classified as neurologically normal at 7.5-8 years. They showed a significant decline in mean IQ scores over time. MRI scans obtained from a subset of children at adolescence were read as normal in approximately 50% of cases and, in the others, there were no consistent relationships between radiological abnormalities and IQ results. Such children can, however, have relatively subtle brain abnormalities that are not seen on conventional MRI, and we hypothesized that these would be related to declines in IQ. Voxel-based morphometry (VBM) analyses of the MRI scans revealed that absolute IQ scores were related to areas in both the parietal and temporal lobes. The analyses also showed that frontal and temporal lobe regions were associated with the decline in VIQ, while occipital and temporal lobe regions (including the hippocampi) were associated with the decline in PIQ. Hippocampal volume measurements were consistent with the VBM findings. We concluded that preterm children are at risk of declining IQ over time even if they have not suffered obvious neurological damage and that the decline is associated with specific neural regions. Whether this is true of children born at >30 weeks gestation and what other factors predispose to this decline have yet to be determined.http://dx.doi.org/10.1093/brain/awh300

Children born preterm provide a fruitful population for studying structure-function relationships because they often have specific functional deficits in the context of normal neurological status. We selected a group of preterm adolescents with deficits in judgment of line orientation. Despite their very low birth weight, all were neurologically normal with no consistent abnormalities on conventional magnetic resonance imaging. However, voxel-based morphometric analysis of their magnetic resonance imaging scans showed areas of decreased gray matter and increased white matter most prominently in right ventral extrastriate cortex, close to an area previously implicated in the line orientation task. We suggest that these anomalies of cortical architecture relate to impaired performance on the line orientation task.http://dx.doi.org/10.1002/ana.10546

Learning difficulties, including problems with numeracy, are common in Western populations. Many children with learning difficulty are survivors of preterm birth. Although some of these children have neurological disabilities, many are neurologically normal, and the latter group provides us with an important opportunity to investigate the neural bases of learning problems. We have conducted a neuroimaging study of adolescent children who had been born preterm at 30 weeks gestation or less, to investigate the relationship between brain structure and a specific difficulty in arithmetic calculation. Using voxel-based morphometry, we have been able to demonstrate that there is an area in the left parietal lobe where children without a deficit in calculation ability have more grey matter than those who do have this deficit. To our knowledge, this is the first report establishing a structural neural correlate of calculation ability in a group of neurologically normal individuals.http://dx.doi.org/10.1093/brain/124.9.1701

Developmental dyscalculia is a significant neural deficit with broad social impact. A number of techniques have been used to identify the brain basis of dyscalculia, and many of these have highlighted the role of the intraparietal sulci and a left fronto-parietal network in the representation of core number skills. These studies offer conflicting explanations of the neurobiological deficits associated with dyscalculia, and to date few studies have elucidated the timeline of cortical changes involved. Here we report a volumetric study comparing well-characterized dyscalculic learners aged from 8 to 14 years with tightly matched controls. Using automated cortical parcellation of anatomical MRI, we show that the posterior parietal and fronto-parietal systems in dyscalculia may undergo abnormal development during the pre-teenage and teenage years. As a result, the present study more clearly characterizes the underlying neural basis of dyscalculia than previous studies have hitherto achieved.

Previous research provides evidence for a dissociable embodied route to spatial perspective-taking that is under strategic control. The present experiment investigated further the influence of strategy on spatial perspective-taking by assessing whether participants may also elect to employ a separable “disembodied” route loading on inhibitory control mechanisms. Participants (N=92) undertook both the “own body transformation” (OBT) perspective-taking task, requiring speeded spatial judgments made from the perspective of an observed figure, and a control task measuring ability to inhibit spatially compatible responses in the absence of a figure. Perspective-taking performance was found to be related to performance on the response inhibition control task, in that participants who tended to take longer to adopt a new perspective also tended to show a greater elevation in response times when inhibiting spatially compatible responses. This relationship was restricted to those participants reporting that they adopted the perspective of another by reversing left and right whenever confronted with a front-view figure; it was absent in those participants who reported perspective-taking by mentally transforming their spatial orientation to align with that of the figure. Combined with previously published results, these findings complete a double dissociation between embodied and disembodied routes to spatial perspective-taking, implying that spatial perspective-taking is subject to modulation by strategy, and suggesting that embodied routes to perspective-taking may place minimal demands on domain general executive functions.

Edmonds,C.J. & Pring, L. (2006). Generating inferences from written and spoken language: a comparison of children with visual impairment and children with sight. British Journal of Developmental Psychology, 24, 337-351.

The two experiments reported here investigated the ability of sighted children and children with visual impairment to comprehend text and, in particular, to draw inferences both while reading and while listening. Children were assigned into ‘comprehension skill’ groups, depending on the degree to which their reading comprehension skill was in line with that predicted by their decoding skill. They then read (either print or Braille) and listened to a series of novel short stories. These were then followed by a series of questions, which required either the generation of an inference, or an answer that could be taken literally from the text. The results suggest that children with and without sight are comparable in their ability to draw inferences, and that children with visual impairment show an advantage for literal questions under auditory presentation.

Edmonds, C.J. & Jeffes, B. Does having a drink help you think? 6–7 year old children show improvements in cognitive performance from baseline to test after having a drink of water. Appetite, 53, 469-472.

Edmonds, C.J.& Burford, D. (2009). Should children drink more water? The effects of drinking water on cognition in children. Appetite, 52, 776-779.

Edmonds,C.J. & Pring, L. (2006). Generating inferences from written and spoken language: a comparison of children with visual impairment and children with sight. British Journal of Developmental Psychology, 24, 337-351.